SYNTHESIS OF ULTRAFINE PARTICLES OF MAGNETITE BY HOMOGENEOUS PRECIPITATION METHOD

Magnetite was prepared from the mixed solution of FeCl2.4H2O and FeCl3.6H2O utilizing the hydrolysis of urea. The ultrafine particles of magnetite were prepared by addition of sodium dodecyl sulfate (SDS) as anion surface active agent into the above mixed solution. The effects of amount of SDS on the particle size were investigated. In the initial stage of the reaction, beta-FeO(OH) was obtained by hydrolysis of Fe3+ ions and it was transformed to Fe3O4 at pH 5.0. The particles were obtained as the suspended solution in water base, since their surfaces were protected by SDS. A part of the ultrafine particles was separated by centrifuging at 15000 rpm for 3 h and dried in a vacuum desiccator at room temperature. The SDS content of the ultrafine particles obtained was about 15.9 wt%, magnetic susceptibility was 30.5 emu/g and coercive force was 0.96 Oe. The size of the ultrafine particles was ranged from 30 nm to 80 nm (average size 50 nm). The ultrafine particles of magnetite was easily prepared and the magnetic fluid of water base was prepared by condensing or by centrifuzing the reaction solution at one step operation.